Systems and methods for verifying documents

ABSTRACT

Abstract of Disclosure 
     Systems and methods for verifying a document.  A document having an encoded document data portion that includes assist information and at least one digitally-signed appended one-way hash is inputted.  The encoded document data file is decoded and  a representation is recovered using the assist information.  A verification one-way hash is generated from the recovered representation.  The verification one-way hash is then compared to the appended one way hash and the authenticity of the document is verified based on the results of the comparison.

Background of the Invention Field of Invention

[0001] This invention is directed to systems and methods for verifyingdocuments.

Description of Related Art

[0002] There are a number of situations where a sender transmits adocument to a receiver and wants to assure the receiver that thedocument has not been altered during the transmission. In other words,the sender wants to authenticate the document.

[0003] Paper documents are traditionally authenticated either throughelaborate printing techniques, such as, for example, money, or throughtrusted signatures and stamps, such as, for example, notarizing by apublic notary. The signing and verifying processes of these currentmethods are not automated and require human intervention. Nor are theseprocesses very reliable.

[0004] There are more recent methods that work on digital document data.During verification, these methods are applied to paper documents byacquiring a scanned image of the printed authenticated document. Theresulting scanned image is then verified using some known verificationscheme. These techniques, unfortunately, do not work well because, whenthe document is scanned by the receiver, the resulting scanned imageusually differs from the original document content used duringauthentication. This occurs due to the noise inherent in scanning adocument. The noise introduced by scanning makes it difficult toconstruct an authentication scheme that is resilient in view of thenoise.

[0005] A method that authenticates photo-identification cards and has tocope with noise being introduced due to scanning is disclosed in "SecureIdentification Documents Via Pattern Recognition and Public-KeyCryptography", by L. O'Gorman et al., IEEE Transactions on PatternAnalysis and Machine Intelligence, Vol. 20, No. 10, pages 1097-1102,October 1998. However, the authentication signature disclosed byO"Gorman et al. has a file size that is linear to the size of thephotograph. This method does not scale well as the size of a documentincreases. The method disclosed in O'Gorman et al. would create anauthentication file that would be large in comparison to the document.This tends to render the O'Gorman et al. method inefficient.

Summary of the Invention

[0006] Due to the presence of noise in the scanning process of hard copydocuments, conventional authenticating schemes cannot guarantee that theauthenticated document is unchanged.

[0007] This invention provides systems and methods for authenticating arepresentation of at least a document.

[0008] This invention separately provides systems and methods thatappend a file to a document that allows a receiver to subsequentlyverify a representation of at least a portion of the document based onthe appended file.

[0009] This invention separately provides systems and methods thatappend a file to a document that allows a receiver to reliably recreatea representation of at least a portion of the document based on theappended file.

[0010] This invention separately provides systems and methods fordetermining a representation of at least a portion of a document. Thisinvention separately provides systems and methods for generating assistinformation from the representation that can be used to ensure that,during verification, the representation will be accurately recreated.This invention separately provides systems and methods for inputting therepresentation and the assist information into a hash function togenerate a one-way hash of the representation and the assistinformation. This invention separately provides systems and methods fordigitally signing the hash of the representation and the assistinformation, and appending the assist information and thedigitally-signed hash of the representation and the assist informationto the document.

[0011] This invention separately provides systems and methods forverifying a document by obtaining assist information and thedigitally-signed hash of a representation of the document and the assistinformation that has been appended to the document. This inventionseparately provides systems and methods for reliably recovering therepresentation of at least a portion of the document using the assistinformation. This invention separately provides systems and methods forinputting the representation and the assist information into a hashfunction to generate a one-way hash of the representation and the assistinformation. This invention separately provides systems and methods forverifying the digital signatures used to create the digitally-signedassist information and hash appended to the document, and comparing thehash generated from the recovered representation and the assistinformation to the hash of the representation and the assist informationthat was appended to the document being verified.

[0012] This invention separately provides systems and methods fordetermining a representation of at least a portion of a document. Thisinvention separately provides systems and methods for inputting arepresentation into a hash function to generate a one-way hash of therepresentation. This invention separately provides systems and methodsfor generating assist information from the representation that can beused to ensure that, during verification, the representation and thehash of the representation will be accurately recreated. This inventionseparately provides systems and methods for digitally signing the hashof the representation and/or the assist information, and appending thedigitally-signed hash of the representation and/or the assistinformation to the document.

[0013] This invention separately provides systems and methods forverifying a document by obtaining the digitally-signed assistinformation and hash of a representation of the document that has beenappended to the document. This invention separately provides systems andmethods for verifying the digital signatures used to create thedigitally-signed assist information and hash appended to the document.This invention separately provides systems and methods for reliablyrecovering the representation of at least a portion of the documentusing the assist information. This invention separately provides systemsand methods for inputting the representation into a hash function togenerate a one-way hash of the representation, and comparing the hashgenerated from the recovered representation to the hash that wasappended to the document being verified.

[0014] This invention separately provides systems and methods thatgenerate a self-contained notarized document where verification does notrequire reference to a remote digital copy of the document.

[0015] In various exemplary embodiments of the systems and methodsaccording to this invention, a representation of at least a portion of adocument is determined. Assist information for the representation isgenerated that can be used to ensure that, during verification, therepresentation will be accurately recreated. In various exemplaryembodiments of the systems and methods according to this invention ,therepresentation and the assist information are input into a hash functionto generate a one-way hash of the representation and the assistinformation. In various exemplary embodiments of the systems and methodsaccording to this invention, the hash of the representation and theassist information are digitally signed. In various exemplaryembodiments of the systems and methods according to this invention, theassist information and the digitally-signed hash of the representationand the assist information are appended to the document.

[0016] In various exemplary embodiments of the systems and methodsaccording to this invention, a document is verified by obtaining assistinformation and the digitally-signed hash of a representation of thedocument and the assist information that has been appended to thedocument. The obtained assist information is used to reliably recoverthe representation of at least a portion of the document. Therepresentation and the assist information are input into a hash functionto generate a one-way hash of the representation and the assistinformation. In various exemplary embodiments of the systems and methodsaccording to this invention, at some earlier time, the digitally-signedhash and assist information appended to the document being verified werechecked to verify the digital signature. The hash and assist informationgenerated from the recovered representation are then compared to thehash and assist information that was appended to the document beingverified. If they are sufficiently close, the document being verified isauthenticated.

[0017] In various other exemplary embodiments of the systems and methodsaccording to this invention, document authentication is accomplished byacquiring document data of a document. The acquired document data can beone or more portions of the contents of the document. A representationof at least a portion of the document is then determined from theacquired document data, and assist information on how to reliablyreproduce the determined representation is generate from the acquireddocument data. A one-way hash function is then applied to the determinedrepresentation to obtain a hash of the determined representation. Thehash and/or the assist information are digitally signed and thenappended to the document.

[0018] In various other exemplary embodiments of the systems and methodsaccording to this invention, document verification is accomplished byacquiring document image data from a copy of the document. The signatureused to sign the digitally-signed hash and/or the assist information isdecoded from the acquired document image data. The signature used tosign the digitally-signed hash and/or the assist information is thenverified. If the signature is valid, the representation of the documentis determined using the assist information appended to the document.That is, the assist information is used to recover the determinedrepresentation. The one-way hash function is then used to generate thehash of the recovered representation. The obtained hash is then comparedto hash that was appended to the copy of the document. If the hashes donot match, the document is determined to have been altered sometimesafter the hash of the representation was generated and appended to thedocument, i.e., the document is not authentic. Otherwise, the documentcan be considered to be authentic.

[0019] In various exemplary embodiments, the determined representationof the document is one or more strings of text. In various exemplaryembodiments, the strings of text are ASCII text strings. In variousother exemplary embodiments, the determined representation includeslocations and/or features of connected components occurring in thedocument image. In various exemplary embodiments, the locations and/orfeatures of connected components include positions of centroids, shapes,membership thresholds, and/or sizes of the connected components.

[0020] These and other features and advantages of this invention aredescribed in, or are apparent from, the following detailed descriptionof various exemplary embodiments of the systems and methods according tothis invention.

Brief Description of the Drawings

[0021] Various exemplary embodiments of this invention will be describedin detail, with reference to the following figures, wherein:

[0022]Fig. 1 is a flowchart outlining a first exemplary embodiment of amethod for authenticating a document according to this invention;

[0023]Fig. 2 is a flowchart outlining a first exemplary embodiment of amethod for verifying a document according to this inventioncorresponding to the authentication method outlined in Fig. 1;

[0024]Fig. 3 is a flowchart outlining a second exemplary embodiment of amethod for authenticating a document according to this invention;

[0025]Fig. 4 is a flowchart outlining a second exemplary embodiment of amethod for verifying a document according to this inventioncorresponding to the authentication method outlined in Fig. 3;

[0026]Fig. 5 is a block diagram of one exemplary embodiment of adocument authentication generating device according to this invention;and

[0027]Fig. 6 is a block diagram of one exemplary embodiment of adocument verification device according to this invention;

Detailed Description of Exemplary Embodiments

[0028] As used herein, the term "authenticate" will refer to generatingauthentication information for inclusion in a document. This term canalso encompass as the process of generating an on-paper signature forthe document. The term "verify" is used herein to refer to the processof checking the document and the included authenticating information todetermine if the document is authentic.

[0029] Due to the presence of noise in the scanning process of hard copydocuments, conventional digital authenticating schemes cannot guaranteethat the authenticated document is unchanged. This invention providessystems and methods for authenticating and verifying documents to detectsuch changes or confirm that the document is unchanged. The variousexemplary embodiments of the systems and methods according to thisinvention will detect substantially all changes to the representation.The choice of representation determines what is considered to besignificant for any particular document. For example, if changes to thetext are considered significant, a suitable representation would be theASCII text of the document. For black and white document, one may alsocare about changes in positions of characters. In this case, thisinformation can also be included in the representation. Therepresentation may focus on specific portions of the document.

[0030] In various exemplary embodiments of the systems and methodsaccording to this invention, a signer or sender of a document createsassist information, which is, for example, stored in a file. The assistinformation will include information and/or hints usable by the verifierand/or receiver to reliably recover a representation of at least aportion of the document that was used in generating a hash that isappended to the authenticated document. The hash can optionally includethe assist information.

[0031] In some form, both the representation and the assist informationare digitally signed. In various exemplary embodiments, a hash of boththe representation and the assist information is generated. This hash isthen digitally signed and appended, with an unsigned copy of the assistinformation, to the document data. In various other exemplaryembodiments, a hash of just the representation is generated. The assistinformation and this hash are then digitally signed and appended to thedocument data. In still various other exemplary embodiments, a hash ofjust the representation is generated. Then, another hash of just theassist information is generated. These two hashes are then digitallysigned and appended, with an unsigned copy of the assist information, tothe document data. The digitally-signed hash and assist information, orthe unsigned assist information and the digitally-signed hash, areencoded into bar codes, glyph-blocks or the like. The bar codes, glyphblocks or the like are then printed on a copy of the document. Thedocument is then transmitted to the receiver and/or to the verifier.

[0032] Upon receiving the document, if the appended data is encoded, thereceiver and/or the verifier first decodes the appended one or moredigitally signed hashes, and the appended assist information, which mayor may not be digitally signed. After the appended data is decoded, ifnecessary, the verifier attempts to verify that the sender or signercreated the digital signature. After the digital signature is verified,the representation will be determined using the assist information sothat the representation is reliably recovered. In various exemplaryembodiments where the assist information is not digitally signed, theassist information can be used without first verifying the digitalsignature. In such cases, verifying the digital signature can bedelayed.

[0033] In various exemplary embodiments, the verifier will generate ahash based on the recovered representation, which, in view of the assistinformation, should be the same representation of the document as usedby the sender. In various other exemplary embodiments, the hash will begenerated based on the representation and the assist information. Instill other various exemplary embodiments, two hashes, one generatedbased on just the representation, and another based just on the assistinformation, can be generated. If the one or more hashes generated bythe receiver and/or the verifier are the same as the one or more hashesprovided by the sender and/or the signer, then the document has not beenaltered during transmission. If the values are different, then thereceiver and/or the verifier determine that the document has beenaltered since it was digitally signed by the signer.

[0034]Fig. 1 is a flowchart outlining a first exemplary embodiment of amethod for authenticating a document according to this invention. Asshown in Fig. 1, operation of the method begins in step S100, andcontinues to step S110, where the document data to be authenticated bymodifying the document data or a copy of the document to containauthentication information is input. Next, in step S120, arepresentation of the document is determined. Then, in step S130, assistinformation usable to reliably recover the determined representation isgenerated. Operation then continues to step S140.

[0035] In step S140, a one-way hash of the assist information and therepresentation is generated. Next, in step S150, the one-way hash of theassist information and the representation is digitally signed. Then, instep S160, the assist information and the digitally signed one-way hashare appended to document data, or to a tangible copy of the document, tosign and/or authenticate the document. Operation then continues to stepS170, where operation of the method ends. In various exemplaryembodiments, the assist information and the digitally-signed one-wayhash are encoded using glyphs, bar-codes, or the like before they areappended to the document data or to the tangible copy of the document.

[0036]Fig. 2 is a flowchart outlining a first exemplary embodiment of amethod for verifying a document according to this invention. As shown inFig. 2, operation of the method begins in step S200, and continues tostep S210, where a notarized, or signed or authenticated document, towhich an encoded document data file having assist information and adigitally signed one-way hash has been appended, is input. Then, in stepS220, the encoded appended assist information and one-way hash isdecoded. Next, in step S230, the assist information is used to recoverthe desired representation of the document from the input document data.Operation then continues to step S240.

[0037] In step S240, a verification one-way hash is generated from therecovered representation and from the assist information. Next, in stepS250, the digital signature used to digitally sign the appended one-wayhash of the representation and the assist information is analyzed todetermine if it is a valid signature. Then, in step S260, adetermination is made whether the digital signature is valid. If thedigital signature is a valid signature, operation continues to stepS270. Otherwise, operation jumps to step S290.

[0038] In step S270, the verification one-way hash generated in stepS240 is compared to the appended one-way hash. Then, in step S280, basedon the comparison, a determination is made whether the document has beenaltered since it was authenticated. If so, operation continues to stepS290. Otherwise, operation jumps to step S300.

[0039] In step S290, an indication is output that the digital signatureused to sign the assist channel is not the correct digital signature forthe person purported to have signed the appended data or that thecomparison failed. Operation then jumps to step S310.

[0040] In contrast, in step S300, an indication is output that thedocument can be authenticated and thus is probably genuine. Operationthen continues to step S310, where operation of the method ends.

[0041]Fig. 3 is a flowchart outlining a second exemplary embodiment of amethod for authenticating a document according to this invention. Asshown in Fig. 3, operation of the method begins in step S1000, andcontinues to step S1010, where the document data to be authenticated bymodifying the document data or a copy of the document to containauthentication information is input. Next, in step S1020, arepresentation of the document is determined. Operation then continuesto step S1030.

[0042] In step S1030, assist information usable to reliably recover thedetermined representation is generated. Next, in step S1040, a one-wayhash of the representation is generated. It should be appreciated thatsteps S1030 and S1040 can be performed in the opposite order, orsimultaneously. Then, in step S1050, the assist information and theone-way hash of the representation is digitally signed. Then, in stepS1060, the digitally signed the assist information and the one-way hashof the representation are appended to document data, or to a tangiblecopy of the document, to sign and/or authenticate the document.Operation then continues to step S1070, where operation on the methodends. In various exemplary embodiments, the digitally-signed assistinformation and one-way hash are encoded using glyphs, bar-codes, or thelike before they are appended to the document data or to the tangiblecopy of the document.

[0043]Fig. 4 is a flowchart outlining a first exemplary embodiment of amethod for verifying a document according to this invention. As shown inFig. 4, operation of the method begins in step S1100, and continues tostep S1110, where a notarized, or signed or authenticated document, towhich an encoded document data file having digitally-signed assistinformation and a one-way hash have been appended, is input. Then, instep S1120, the encoded appended assist information and one-way hash isdecoded. Next, in step S1130, the digital signature used to digitallysign the appended assist information and one-way hash of therepresentation is analyzed to determine if it is a valid signature.Then, in step S1140, a determination is made whether the digitalsignature is valid. If the digital signature is a valid signature,operation continues to step S1150. Otherwise, operation jumps to stepS1190.

[0044] In step S1150, the assist information is used to recover thedesired representation of the document from the input document data.Next, in step S1160, a verification one-way hash is generated from therecovered representation. Then, in step S1170, the verification one-wayhash generated in step S1160 is compared to the appended one-way hash.Next, in step S1180, based on the comparison, a determination is madewhether the document has been altered since the authenticationinformation was generated. If so, operation continues to step S1190.Otherwise, operation jumps to step S1200.

[0045] In step S1190, an indication is output that the digital signatureused to sign the assist channel is not the correct digital signature forthe person purported to have signed the appended data or that thecomparison failed. Operation then jumps to step S1210. In contrast, instep S1200, an indication is output that the document can beauthenticated and thus is probably genuine. Operation then continues tostep S1210, where operation of the method ends.

[0046]Fig. 5 shows one exemplary embodiment of a document authenticationdevice 100 implementing the systems and methods for documentauthentication according to this invention. As shown in Fig. 5, thedocument authentication device 100 includes an input/output interface105, a controller 110, a memory 120, a representation determiningcircuit, routine or manager 130, a assist information determiningcircuit, routine or manager 140, a hash value generating circuit,routine or manager 150, a data compressing circuit, routine or manager155, a signature generating circuit, routine or manager 160, and a dataappending circuit, routine or manager 170, interconnected by acontrol/data bus 115.

[0047] The memory 120 includes a document image data portion 121, anassist information portion 122 and a representation portion 123. Itshould be appreciated that these are functional and not physicalportions of the memory 120. In various exemplary embodiments, the assistinformation can include any information usable to reliably recreate anydesired representation determined by the representation determiningcircuit routine or manager 130.

[0048] As shown in Fig. 5, an image data source 200, one or more inputdevices 300, a display device 400 and/or a printer 500 can be connectedto the document authentication device 100 over links 205, 305, 405 and505, respectively.

[0049]Fig. 6 shows one exemplary embodiment of a document verificationdevice 600 implementing the systems and methods for documentverification according to this invention. As shown in Fig. 6, thedocument verification device 600 includes an input/output interface 605,a controller 610, a memory 620, a signature verification circuit,routine or manager 630, a representation determining circuit, routine ormanager 640, a hash value generating circuit, routine or manager 650 anda comparing circuit, routine or manager 660, interconnected by acontrol/data bus 615.

[0050] As shown in Figs 5 and 6, an image data source 200, one or moreinput devices 300, a display device 400 and a printer 500 are connectedto the document authentication device 600 over links 205, 305, 405 and505, respectively.

[0051] In general, the image data source 200 shown in Figs. 5 and 6 canbe any one of a number of different sources, such as general-purposecomputer, a scanner, a digital copier, a facsimile device that issuitable for generating electronic image data, or a device suitable forstoring and/or transmitting electronic image data, such as a client orserver of a network, or the Internet, and especially the World Wide Web.For example, the image data source 200 may be a scanner, or data carriersuch as a magnetic storage disk, CD-ROM or the like, or host computer,that contains document data and/or scanned image data.

[0052] In general, the image data source 200 can be any known or laterdeveloped source that is capable of providing document data and/or imagedata to the document authentication device 100 and the documentverification device 600, of this invention respectively. It should beunderstood that the image data source 200 of Figs. 5 and 6 does not needto be the same type of device.

[0053] The image data source 200 can be integrated with the documentauthentication device 100, such as in a digital copier having anintegrated scanner. Alternatively, the link 205 connecting the imagedata source 200 to the document authentication devices 100 can be aconnection device, such as a modem, a local area network, a wide areanetwork, and intranet, the Internet, any other distributed processingnetwork, or any other known or later developed connection device.Similar relative connections may be made between the image data source200 and the document verification device 600. Further, the image datasource 200 is also adapted to provide a data file that is appended tothe document by the signer. The appended data may be encoded usingglyphs, a bar code, or any other known or later-developed technique forencoding data into a printed image.

[0054] Each of the links 205-505 can be any known or later-developeddevice or system for connecting the respective devices to the documentauthentication device 100 and the document verification device 600,respectively, including a direct cable connection, a connection over awide area network or a local area network, a connection over anintranet, a connection of the Internet, or a connection over any otherdistributed processing network or system. It should be appreciated thatany of these connectors can be either wired or wireless. In general,each of the links 205, 305, 405, 505 can be any known or later-developedconnection system or structure usable to connect the respective devicesto the document authentication device 100 or the document verificationdevice 600, respectively. It should be understood that the links 205,305, 405, 505 do not need to be of the same type.

[0055] Each of the respective one or more input devices 300 may be anycombination of one or more input devices, such as a keyboard, a mouse, ajoy stick, a trackball, a touch pad, a touch screen, a pen-based system,a microphone and associated voice recognition software, or any otherknown or later-developed device for inputting user commands to thedocument authentication device 100 and the document verification device600, respectively. It should be understood that the respective one ormore input devices 300 of Figs. 5 and 6 do not need to be the same typeof device.

[0056] The display device 400 may be a monitor that is capable ofdisplaying an electronic version of the resulting document image forviewing or displaying any other intermediary steps of the documentauthentication and verification process. The display 400 is optional andthus may be omitted. It should be understood that the display 400 ofFigs. 5 and 6 does not need to be the same type of device. The printer500 can be any known or later-developed image-forming device that iscapable of printing a tangible copy of an image. It should also beunderstood that the printer 500 of Figs. 5 and 6 do not need to be thesame type of device.

[0057] It should be appreciated that the image data source 200, the oneor more input devices 300, the display 400, and the printer 500 do nothave to be locally associated with the document authentication device100. Furthermore, it should be appreciated that the documentauthentication device 100, and any one or more of the image data source200, the one or more input devices 300, the display 400 and the printer500 can be elements integrated into a single device, such as aphotocopier or the like. Furthermore, it should also be appreciated thatany number of these devices may be integrated into a single device tocooperate with the remaining devices.

[0058] As shown in Figs. 5 and 6, the memory 120 can be implementedusing any appropriate combination of alterable, volatile, ornon-volatile memory or non-alterable, or fixed memory. The alterablememory, whether volatile, or non-volatile, can be implemented using anyone or more of static or dynamic RAM, a floppy disk and disk drive, awritable or rewritable optical disk and disk drive, a hard drive, flashmemory or the like. Similarly, the non-alterable or fixed memory can beimplemented using any one or more of ROM, PROM, EPROM, EEPROM, and gapsan optical ROM disk, such as a CD-ROM or DVD-ROM disk, and disk drive orthe like.

[0059] Each of the various embodiments of the document authenticationdevice 100 and the document verification device 600 can be implementedas software executing on a programmed general purpose computer, aspecial purpose computer, a microprocessor or the like. Alternatively,each of the various embodiments of the document authentication device100 and the document verification device 600 can be implemented as aroutine embedded in a printer driver, as a resource residing on aserver, or the like. Each of the various embodiments of the documentauthentication device 100 and the document verification device 600 canalso be implemented by physically incorporating that device into asoftware and/or hardware system, such as the hardware and softwaresystem of a printer or a digital photocopier. It should be understoodthat each of the various embodiments of the document authenticationdevice 100 and the document verification device 600 do not need to beimplemented the same way.

[0060] It should also be understood that each of the circuits, routinesor managers shown in Figs. 5 and 6 can be implemented as portions of asuitably programmed general-purpose computer. Alternatively, each of thecircuits, routines or managers shown in Figs. 5 and 6 can be implementedas physically distinct hardware circuits within an ASIC, using a digitalsignal processor (DSP) or using a FPGA, a PDL, a PLA and/or a PAL, orusing discrete logic elements or discrete circuit elements. Theparticular form each of the circuits, routines or managers shown inFigs. 5 and 6 will take is a design choice and will be obvious andpredicable to those skilled in the art. It should be appreciated thatthe circuits, routines or managers shown in Figs. 5 and 6 do not need tobe of the same design.

[0061] When operating the document authentication device 100, a userinstructs the document authentication device 100 through one or more ofthe one or more input devices 300 over the link 305 to notarize orauthenticate a document, as shown in Fig. 5. Document data, such aselectronic document data, such as ASCII text data, or an image of thedocument, to be notarized or authenticated is received by the documentauthentication device 100 from the image data source 200 via the link205 at the input/output interface 105. The input/output interface 105inputs the input image data, and, under direction of the controller 110,forwards it to the document image data portion of the memory 120.

[0062] The representation determining circuit, routine or manager 130then retrieves the image data from the image data portion 121 of thememory 120 under control of the controller 110 and determines one ormore portions of the document that will be used as a representation ofthe document when authenticating and verifying the document. It shouldbe appreciated that any one or more known or later developed types ofrepresentation can be determined by the representation determiningcircuit, routine or manager 130, and in any desired combination. Invarious exemplary embodiments, the representation can be ASCII text dataof one or more lines of electronic image data selected from the documentdata. In various other exemplary embodiments, the representation can beany number of document features obtainable from connected componentspresent in the document data. Various exemplary embodiments of documentfeatures obtainable from connected components present in the documentdata are disclosed in U.S. Patent application serial number (Attorneydocket number 107151), filed herewith and incorporated herein byreference in its entirety.

[0063] In a first exemplary embodiment of the operation of the documentauthentication device 100, the determined representation stored in therepresentation portion 123 of the memory 120 is then output, undercontrol of the controller 110 to the assist information determiningcircuit, routine or manger 140. Alternatively, the representationdetermining circuit, routine or manager 130 can directly output, undercontrol of the controller 110, the determined representation to theassist information determining circuit as well as to the representationportion 122 of the memory 120.

[0064] The assist information determining circuit, routine or manager140 inputs the determined representation and determines and outputsassist information about the determined representation to the memory 120to be stored in the assist information portion 122 under control of thecontroller 110. The assist information generated by the assistinformation determining circuit, routine or manager 140 can include anydesired information that will allow the verification device 600 toreliably recover the representation.

[0065] The hash value generating circuit, routine or manager 150 inputsthe representation determined by the representation determining circuitor routine 130 and the assist information generated by the assistinformation generating circuit or routine 140 from the memory 120 anddetermines one or more hash values based on the determinedrepresentation and the generated assist information. The hash valuegenerating circuit, routine or manager 150 outputs the one or more hashvalues to the memory 120, under control of the controller 120, to bestored in any desired portion of the memory 120. In various exemplaryembodiments, the hash value generating circuit, routine or manager 150determines cryptographically secure hash values.

[0066] In various exemplary embodiments, the hash value generatingcircuit, routine or manager 150 determines a hash value using any knownor later-developed hashing technique. In various exemplary embodiments,the hash value generating circuit, routine or manager 150 determines thehash value using a sequential hashing technique.

[0067] The signature generating circuit, routine or manager 165 inputsthe one or more hash values generated from the representation and theassist information stored the memory 120 and digitally signs this data.The digitally-signed one or more hash values are then output, undercontrol of the controller 110, to any desired portion of the memory 120.In various exemplary embodiments, the signature generating circuit,routine or manager 165 uses any known or later-developed digital signingtechnique. In various exemplary embodiments, the signature generatingcircuit, routine or manager 165 uses a known encryption technique todigitally sign the one or more hash values. It should be understood thatthe signature generating circuit routine or manager 165 can optionallybe omitted from the document authentication device 100.

[0068] The data appending circuit, routine or manager 170 inputs thedigitally-signed one or more hash values stored in the memory 120 andthe assist information stored in the assist information portion 122 andappends the input data to the document image data or directly to a copyof the document. In various exemplary embodiments, the data appendingcircuit routine or manger 170 converts digitally-signed one or more hashvalues stored in the memory 120 and the assist information stored in theassist information portion 122 into a format, such as, but not limitedto, data glyphs or bar codes, before it is appended to the documentimage data.

[0069] In various exemplary embodiments, the data appending circuitroutine or manager 170 adds the appended data, whether inmachine-readable format or human-readable format, to the document imagedata stored in the document image data portion 122. In this case, atangible copy of the digitally signed document is generated by printingthe document image data stored in the document image data portion 122.Alternatively, the data appending circuit, routine or manager 170, undercontrol of the controller 110, appends the machine-readable orhuman-readable data to a tangible copy of the document. In this case,the user places a tangible copy of the document on the printer 500. Theprinter 500 then receives the appended machine-readable or humanreadable data from the document authentication device 100 over the link505. The appended data is then added to the original tangible copy ofthe document.

[0070] In a second exemplary embodiment of the operation of the documentauthentication device 100, the determined representation stored in therepresentation portion 123 of the memory 120 is output, under control ofthe controller 110 to both the assist information determining circuit,routine or manger 140 and to the hash value generating circuit, routineor manager 150. Alternatively, the document feature generating circuit,routine or manager 130 can directly output, under control of thecontroller 110, the determined document features to both the documentfeatures information determining circuit and to the hash valuegenerating circuit, routine or manager 150 as well as to therepresentation portion 123 of the memory 120.

[0071] The assist information determining circuit, routine or manager140 inputs the determined representation and determines and outputsassist information about the determined representation to the memory 120to be stored in the assist information portion 122 under control of thecontroller 110. The assist information generated by the assistinformation determining circuit, routine or manager 140 can include anydesired information that will allow the verification system 600 toreliably recover the representation.

[0072] The hash value generating circuit, routine or manager 150 inputsthe representation and determines one or more hash values based on thedetermined representation. The hash value generating circuit, routine ormanager 150 outputs the one or more hash values to the memory 120, undercontrol of the controller 120, to be stored in any desired portion ofthe memory 120. In various exemplary embodiments, the hash valuegenerating circuit, routine or manager 150 determines cryptographicallysecure hash values.

[0073] In various exemplary embodiments, the hash value generatingcircuit, routine or manager 150 determines a hash value using any knownor later-developed hashing technique. In various exemplary embodiments,the hash value generating circuit, routine or manager 150 determines thehash value using a sequential hashing technique.

[0074] The signature generating circuit, routine or manager 165 inputsthe assist information stored in the assist information portion 122 ofthe memory 120 and the one or more hash values generated from therepresentation and digitally signs the assist information and the one ormore hash values. The digitally-signed assist information and one ormore hash values are then output, under control of the controller 110,to any desired portion of the memory 120. In various exemplaryembodiments, the signature generating circuit, routine or manager 165uses any known or later-developed digital signing technique. In variousexemplary embodiments, the signature generating circuit, routine ormanager 165 uses a known encryption technique to digitally sign theassist information and the one or more hash values. It should beunderstood that the signature generating circuit routine or manager 165can optionally be omitted from the document authentication device 100.

[0075] The data appending circuit, routine or manager 170 inputs thedigitally-signed the assist information one or more hash values storedin the memory 120 and stored in the memory 120 and appends the inputdata to the document image data or directly to a copy of the document.In various exemplary embodiments, the data appending circuit routine ormanger 170 converts the digitally-signed the assist information and theone or more hash values stored in the memory 120 into a format, such as,but not limited to, data glyphs or bar codes, before it is appended tothe document image data.

[0076] In various exemplary embodiments, the data appending circuitroutine or manager 170 adds the appended data, whether inmachine-readable format or human-readable format, to the document imagedata stored in the document image data portion 122. In this case, atangible copy of the digitally signed document is generated by printingthe document image data stored in the document image data portion 122.Alternatively, the data appending circuit, routine or manager 170, undercontrol of the controller 110, appends the machine-readable orhuman-readable data to a tangible copy of the document. In this case,the user places a tangible copy of the document on the printer 500. Theprinter 500 then receives the appended machine-readable or humanreadable data from the document authentication device 100 over the link505. The appended data is then added to the original tangible copy ofthe document.

[0077] When operating the document verification device 600, a userinstructs the document verification device 600 through one or more ofthe one or more input devices 300 over the link 305 to verify adocument, as shown in Fig. 6. The document to be verified includesappended data that has been digitally signed and that includes documentfeatures and/or an assist channel. Document image data of the documentto be verified is received by the document verification device 600 fromthe image data source 200 via the link 205 and the input/outputinterface 605. The input/output interface 605 inputs the input imagedata, and under direction of the controller 610, forwards the receiveddocument image data to the document image data portion 621 of the memory620.

[0078] The signature verification circuit, routine or manager 630 inputsthe appended data and decodes it from the machine-readable format intoone or more hash values and assist information. The assist informationis stored into an assist information portion 622 of the memory 620. Theone or more hash values are stored into any desired portion of thememory 120.

[0079] The signature verification circuit, routine or manager 630 checksthe decoded digitally-signed data to verify the digital signature usedto digitally sign the appended data is the correct digital signature forthe purported signer of the document. The signature verificationcircuit, routine or manager 630 can use any known or later-developeddigital signature verification technique to verify that the digitalsignature used to digitally sign the appended data is that of thepurported signer.

[0080] If the digital signature is that of the purported signer, thenthe document verification device 600 has verified that the purportedsigner actually signed and created the digitally-signed appended data.In this case, the document verification device 600 can proceed, byverifying that the received document is substantially identical to thedocument digitally signed by the signer in essentially all significantrespects by determining one or more hash values from the receiveddocument image data based on the assist information contained in theappended data and comparing the one or more verification hash values tothe signer's corresponding one or more hash values contained in theappended data.

[0081] In contrast, in various exemplary embodiments, if the digitalsignature is not that of the purported signer, the document verificationdevice 600 stops the verification process on that document.Alternatively, assuming the appended data can be decrypted in view ofany encryption applied to it, the appended data is analyzed as outlinedabove to verify that the content of the document is substantiallyidentical to the content of the signed document. However, in this case,the document is flagged as having an unverified signature.

[0082] The representation determining circuit, routine or manager 640inputs the document image data and determines, or recovers, a desiredrepresentation of one or more portions of the document image data. Thedetermined representation is stored in the representation portion 623 ofthe memory 620 under control of the controller 610. In various exemplaryembodiments, the representation determining circuit, routine or manager640 additionally or alternatively outputs the determined representationto the hash circuit, routine or manager 650.

[0083] The representation determining circuit, routine or manager 640inputs the document image data and the assist information. Therepresentation determining circuit, routine or manager 640 determineseach desired representation in view of the assist information stored inthe assist information portion 622 to ensure that the recoveredrepresentation generally matches the representation that was determinedfrom the original document data by the document authentication device100 and used by the document authentication device 100 to generate theappended hash values.

[0084] In various exemplary embodiments, the desired representation isan optical character recognition of one or more text strings that occurin the document. U.S. Patent application serial numbers 09/574,268,09/574,270, 09/574,274 and 09/574,406each incorporated herein byreference in its entirety, disclose a number of methods for reliablyrecovering such text strings using optical character recognition andvarious types of assist information. In various other exemplaryembodiments, the desired representation includes various connectedcomponents that occur in the document. The incorporated (Attorney docketnumber 107151) application discloses various methods for reliablyrecovering connected component information using assist information.

[0085] At this point, the document verification device 600 should haveestablished a significant matching of the recovered representation withthe representation as used by the document authentication device 100when generating the one or more hash values. Accordingly, the hash valuegenerating circuit, routine or manager 650 performs exactly the samehashing steps as outlined above with respect to the hash valuegenerating circuit, routine or manager 150 of the documentauthentication device 100.

[0086] In a first exemplary embodiment of the operation of the documentverification device 600, the hash value generating circuit, routine ormanager 650 inputs the recovered representation from the representationportion 623 and the assist information from the assist informationportion 622 of the memory 620 and determines one or more verifier hashvalues from the recovered representation and the assist information. Thehash value generating circuit, routine or manager 650 outputs the one ormore verifier hash values to the memory 620 under control of thecontroller 610. The hash value generating circuit, routine or manager650 determines the one or more verifier hash values using the same knownor later-developed hashing techniques as the hash value generatingcircuit, routine or manager 150. In various exemplary embodiments, thehash value generating circuit, routine or manager 650 determines the oneor more verifier hash values using a sequential hashing technique.

[0087] The hash value comparing circuit, routine or manager 660 inputsone or more verifier hash values and corresponding one or moreauthentication hash values from the memory 620. The hash value comparingcircuit, routine or manager 660 compares each of the one or moreverifier hash value to the corresponding ones of the one or moreauthentication hash values. If the respective hash values are aboutequivalent, then the hash value comparing circuit, routine or manager660 outputs a signal or an indication via the input/output interface 605to the display device 400 over the link 405 and/or to the printer 500over the link 505 that the document is unchanged from the signeddocument image data. If the respective hash values are not aboutequivalent, then the hash value comparing circuit, routine or manager660 outputs, under control of the controller 610, a signal or indicationvia the input/output interface 605 to the display device 400 over thelink 405 and/or to the printer 500 over the link 505 that the documenthas been altered since the authentication hash values were generated.

[0088] It should be appreciated that, since, in the first exemplaryembodiment of the operation of the verification device 600, only thehash of the assist information and the representation is digitallysigned, the signature verification circuit, routine or manager 630 doesnot need to check the signature until just before the hash valuecomparing circuit, routine or manager 660 needs to input the one or moreauthentication hash values. In this case, the digitally-signed hashvalues are stored in the memory 620.

[0089] In a second exemplary embodiment of the operation of the documentverification device 600, the hash value generating circuit, routine ormanager 650 inputs the recovered representation from the representationportion 623 and determines one or more verifier hash values from therecovered representation. The hash value generating circuit, routine ormanager 650 outputs the one or more verifier hash values to the memory620 under control of the controller 610. The hash value generatingcircuit, routine or manager 650 determines the one or more verifier hashvalues using the same known or later-developed hashing techniques as thehash value generating circuit, routine or manager 150. In variousexemplary embodiments, the hash value generating circuit, routine ormanager 650 determines the one or more verifier hash values using asequential hashing technique.

[0090] The hash value comparing circuit, routine or manager 660 inputsone or more verifier hash values and corresponding one or moreauthentication hash values from the memory 620. The hash value comparingcircuit, routine or manager 660 compares each of the one or moreverifier hash value to the corresponding ones of the one or moreauthentication hash values. If the respective hash values are aboutequivalent, then the hash value comparing circuit, routine or manager660 outputs a signal or an indication via the input/output interface 605to the display device 400 over the link 405 and/or to the printer 500over the link 505 that the document is unchanged from the signeddocument image data. If the respective hash values are not aboutequivalent, then the hash value comparing circuit, routine or manager660 outputs, under control of the controller 610, a signal or indicationvia the input/output interface 605 to the display device 400 over thelink 405 and/or to the printer 500 over the link 505 that the documenthas been altered since the authentication hash values were generated.

[0091] While this invention has been described in conjunction with thespecific embodiments outlined above, it is evident that manyalternatives, modifications and variations will be apparent to thoseskilled in the art. Accordingly, the preferred embodiments of theinvention, as set forth above, are intended to be illustrative, notlimiting. Various changes may be made without departing from the spiritand scope of this invention.

What Is Claimed Is
 1. A method for verifying a document, comprising: inputting a document having an encoded document data portion that includes assist information and at least one digitally-signed appended one-way hash; recovering at least one representation of the input document using the assist information; generating at least one verification one-way hash from at least one of the at least one recovered representation; comparing at least one of the at least one verification one-way hash to the corresponding at least one of the at least one appended one-way hash; and verifying an authenticity of the document based on results of the comparison.
 2. The method of claim 1, further comprising, when the assist information is digitally signed, verifying a digital signature of digitally-signed assist information.
 3. The method of claim 2, further comprising verifying a digital signature of the digitally signed one-way hash.
 4. The method of claim 2, further comprising determining whether the digital signature is a valid digital signature.
 5. The method of claim 4, further comprising recovering the at least one representation of the document only when the digital signature of the digitally-signed document is determined to be valid.
 6. The method of claim 4, further comprising, when the signature is determined to be valid, recovering original document data from the decoded document data portion.
 7. The method of claim 2, wherein verifying the authenticity of the document comprises determining whether the document has been altered.
 8. The method of claim 2, wherein verifying the authenticity of the document comprises outputting, based on the results of the comparison, one of an indication that the document is genuine and an indication that the document is not genuine.
 9. The method of claim 2, further comprising decoding the encoded document data portion.
 10. The method of claim 1, further comprising verifying a digital signature of the digitally signed one-way hash.
 11. The method of claim 1, further comprising determining whether the digital signature is a valid digital signature.
 12. The method of claim 11, further comprising recovering the at least one representation of the document only when the digital signature of the digitally-signed document is determined to be valid.
 13. The method of claim 11, further comprising, when the signature is determined to be valid, recovering original document data from the decoded document data portion.
 14. The method of claim 1, wherein verifying the authenticity of the document comprises determining whether the document has been altered.
 15. The method of claim 1, wherein verifying the authenticity of the document comprises outputting, based on the results of the comparison, one of an indication that the document is genuine and an indication that the document is not genuine.
 16. The method of claim 1, further comprising decoding the encoded document data portion.
 17. A document authentication verification system that verifies authentication data for a document, comprising: means for inputting a document having an encoded document data portion that includes assist information and at least one digitally-signed appended one-way hash; a representation generating circuit, routine or application that generates at least one representation of the input document using the assist information; a hash generating circuit, routine or application that generates at least one verification one-way hash from at least one of the at least one generated representation; a hash value comparing circuit, routine or application that compares at least one of the at least one verification one-way hash to the corresponding at least one of the at least one appended one-way hash; and an authenticity verification circuit, routine or application that verifies an authenticity of the document based on results of the comparison.
 18. The document authentication system of claim 17, further comprising a signature verification circuit, routine or application, wherein, when the assist information is digitally signed, the signature verification circuit, routine or application verifies the digital signature of the digitally-signed assist information.
 19. The document authentication system of claim 18, wherein the signature verification circuit, routine or application verifies a digital signature of the digitally-signed one-way hash.
 20. The document authentication system of claim 18, further comprising a signature determining circuit, routine or application that determines whether the digital signature is a valid digital signature.
 21. The document authentication system of claim 18, wherein the authenticity verification circuit, routine or application outputs one of an indication that the document is genuine and an indication that the document is not genuine based on the results of the comparison.
 22. The document authentication system of claim 18, wherein the representation generation circuit, routine or application generates at least one representation of the document only when the signature determining circuit, routine or application determines that the digital signature of the digitally-signed document is valid.
 23. The document authentication system of claim 18, wherein the representation generating circuit, routine or application generates original document data from the decoded document data portion when the signature determining circuit, routine or application determines that the digital signature is valid.
 24. The document authentication system of claim 17, further comprising a signature verification circuit, routine or application that verifies a digital signature of the digitally-signed one-way hash.
 25. The document authentication system of claim 17, further comprising a signature determining circuit, routine or application that determines whether the digital signature is a valid digital signature.
 26. The document authentication system of claim 17, wherein the authenticity verification circuit, routine or application outputs one of an indication that the document is genuine and an indication that the document is not genuine based on the results of the comparison.
 27. The document authentication system of claim 17, wherein the representation generation circuit, routine or application generates at least one representation of the document only when the signature determining circuit, routine or application determines that the digital signature of the digitally-signed document is valid.
 28. The document authentication system of claim 17, wherein the representation generating circuit, routine or application generates original document data from the decoded document data portion when the signature determining circuit, routine or application determines that the digital signature is valid. 